1. Field of the Invention
The invention relates to devices which employ optical fiber; more specifically, the invention relates to a device, system, and method of managing optical fibers in a way to keep them organized and protected from damage.
2. Description of Related Art
Modem computer and telecommunications networks are constantly growing more complex and have an ever-expanding need for bandwidth (the ability to accept, process, and/or transmit information). Many of the components used in such networks utilize optical transceivers and optical fibers as the means of communicating among and within the various components.
One of the ways that optical network components can be made more efficient is by providing them with a greater density of optical transceivers and fibers. One cannot merely increase the density on whim since optical fibers, however small they may be, do occupy space, and the housing or chassis in which they are disposed is finite in volume. Specific and carefully contemplated fiber connection schemes therefore must be employed.
Typically, optical transceivers are mounted in groups on a single card called a line module or line card. Often, optical fibers are connected directly to the transceivers in one of two ways. First, the fiber can pass through the faceplate of the line module and terminate at the transceiver inside the line module. Such a connection system is known as an internal connect scheme. Internal connect schemes are difficult to service since the optical fibers were not easily disconnected from their respective optical transceivers. A second, more common, connect scheme is an external connection scheme in which the optical fiber is connected to the transceiver via connection ports through the exterior of the faceplate of the line module.
Currently, one of the density limitations on a faceplate mounted cable interconnect scheme is the physical size of the connector. The industry standard as of the filing of this application in the United States is the SC style connector. In Europe, the standard connector in many countries is the FC style connector. Both SC and FC connectors are comparatively large compared to recent connectors developed by Lucent Technologies, specifically the LC connector. As fiber optic interconnect density increases, LC connectors gain in popularity, so much so that many component manufacturers are designing fiber optic transceivers that utilize an integral plastic housing with LC connectors (the female side of the connector is mounted to the transceiver and is accessible from outside the line module).
Under an industry multi-source agreement, the small form factor transceiver standard was created and adopted and has been distributed by component manufacturers so that all new small form factor transceivers follow a common package size and interconnect scheme. Many of these new small form factor transceivers are designed with an integral EMI clip that allows the part to be mounted at the front of a given line module (or other circuit pack) and protrude through the front of the equipment faceplate to make cable access easier.
Unfortunately, mounting small form factor transceivers on line module faceplates causes the fiber optic cable to enter the faceplate at an angle of incidence such that it becomes difficult to route the fiber away from the source and, at the same time, prevent the telecommunications equipment chassis doors from crushing the fiber optic cable when closed. Additionally, as the density of the cables increases, it becomes increasingly more difficult for technicians to service the equipment without disrupting cables adjacent to the cables that need to be serviced. To address this problem, some cable manufacturers have developed custom boots integral with the cable assembly that bend the cable so as to avoid interference with the door of the chassis. However, current industry solutions are designed to exit the small form factor transceiver orthogonal to (i.e., straight out from) the module. These boots can be rotated slightly but will interfere with adjacent boots when the angle becomes too great.
One contemporary device has been produced by Siecor Operations. It is a stainless steel clip which fits along the base of the optical fiber and fits under the connector boot of an SC or FC connector. It acts like a spine for the cable, bending it roughly 90xc2x0. However, it has several problems associated with it. First, it is completely incompatible with LC connectors that do not have specific Siecor boots attached thereon. Second, it does not actually cover a significant amount of the cable; as a result, even though the cable is kept fairly rigid, the clip does not actually protect the fiber optic cable. A sharp blow by either the door of the chassis of a networking device or by an incautious technician can still damage the optical fiber cable. Finally, there is no way to tell precisely where on the optical fiber this device is supposed to be placed for optimal bending.
Another such contemporary device is produced by Corning Cable Systems and is a plastic clip compatible with LC connectors similar to the stainless steel Siecor clip described above. The Corning clip fails to support the bent portion of the fiber throughout the entire section of bent fiber. As such, the fiber may not lay properly in the Corning clip. Also, the Corning clip appears to be less than reliable when used with smaller width optical fibers. Specifically, jacketed optical fiber commonly comes in a variety of diameters, from 1.6 to 3.0 mm. The Corning clip does not hold fibers in the smaller end of that width range very securely at all.
Other similar contemporary fiber bending devices require a stiffening rib to provide support and strength for the fiber bender. These stiffening ribs increase the size of the fiber bender; as a result, adjacent fibers connected to the same LC connector (which typically accommodates two fibers very close together) are pushed apart, causing undue stress on the connector and thus the transceiver.
Other companies utilize external faceplate interconnect schemes which cannot utilize the current industry solutions. Moreover, some of the equipment already in the field utilizes LC connectors which are mounted internally to the faceplate where bending the cable is not required. A solution must be available which is compatible with LC connectors and yet removable so that existing networking devices that do not require fiber bending are still serviceable, bearing in mind that optical fibers are brittle and may break during removal, insertion, or servicing of line modules.
The invention is a fiber bending apparatus for bending an optical fiber in a networking device. It has an arcuate main body having a first end, a second end, and a central channel. The central channel is preferably disposed along the side of the main body substantially perpendicular to the curvature of the main body (i.e., the fiber bender curves up and away from a module faceplate and the channel is on the left or right side of the bender). The provision of the channel on the side of the bender allows the bender to support the bent fiber throughout the entire length of the bent portion of the fiber. If the channel were disposed on the top of the apparatus along the curvature of the bend of the main body, any fiber disposed therein might not lie flat along the bottom of the channel. However, placing the channel on the side of the apparatus provides support from both above and below the fiber via the walls of the main body.
The first end is shaped to receive in the central channel an optical fiber and the second end is shaped to receive in the central channel a connector boot disposed around the optical fiber. The fiber bending apparatus bends a fiber disposed in the central channel away from a front service (e.g., an enclosure door) of the networking device, and preferably bends the fiber substantially orthogonal to a direction from which the fiber is connected to the line module. The arcuate main body has a radius of curvature substantially equal to the minimum industry-recommended bend radius for optical fiber. In this way, the fiber bender acts to provide as much clearance as possible between the optical fiber emerging from the line module and the chassis.
The fiber bending apparatus preferably includes a shoulder formed in the central channel at a predetermined distance from the second end. The shoulder narrows the central channel. When a connector boot is inserted into the second end of the apparatus, the shoulder is engaged by the fiber connector boot to thereby prevent the connector boot from being inserted into the fiber bending apparatus beyond the predetermined distance. In this way, the inventive fiber bender has a depth gauge to prevent the connector boot from being inserted too far into the bender. This feature is important, since should the connector be inserted too far into the bender, two fiber benders on adjacent optical fibers would interfere with each other and push the two optical fibers apart; this would put undue stress on both the optical fibers and the optical transceiver.
Preferably, at least the second end of the main body is resilient and forms a friction fit with a connector boot inserted therein. At least one retaining projection is formed in the central channel. Projections formed near the first end engage the optical fiber and help to prevent the fiber bending apparatus from easily falling off of the optical fiber, while projections formed near the second end engage the connector boot and also help to prevent the fiber bending apparatus from easily falling off of the optical fiber.
The invention also includes an optical fiber management system. An outer chassis is provided with inner support structure mounted within the chassis. A plurality of line modules are inserted and supported by the support structure, each of the line modules having a plurality of optical transducers connected to female connectors. A plurality of optical fibers each respectively terminating in connector boots and male connectors are matingly engageable with the female connectors. A plurality of fiber bending devices similar to those described above, are selectively attachable to the optical fibers. Each of the fiber bending devices includes an arcuate main body having a first end, a second end, and a central channel. The first end is shaped to receive in the central channel one of the optical fibers and the second end is shaped to receive in the central channel one of the connector boots disposed around the one of the optical fibers. The plurality of fiber bending devices bend the optical fibers away from the chassis substantially orthogonal to a direction from which the optical fibers are connected to the line modules.
The invention also includes a method of organizing and managing optical fibers in a networking device utilizing the inventive fiber bender discussed above.